Bearings for electrical parts of automobiles such as an alternator; an electromagnetic clutch for a car air conditioner, an intermediate pulley and an electric fan motor, auxiliaries of engine and the like are used under severe environments such as high temperature, high speed, high load and vibration environment. In the bearings used in such severe environments, spalling of the fixed ring surface of the bearing is recognized in a period of time being as extremely short as 1/10 or less of a calculated service life theoretically estimated. It is known that the reason for this is such that an excessive tangential force as well as slipping arises under severe working conditions between the roiling element and the rolling contact surfaces of the inner and outer rings, thereby causing the spalling in an early stage of the use.
In this connection, grease for solving such a problem as mentioned above has been reported. For example, JP 61-155496 A discloses grease prepared using, as a thickener, a diurea compound obtained by allowing an amine mixture comprising alkylphenylamine, an alkyl group of which has 8 to 16 carbon atoms, and cyclohexylamine in a molar ratio of 1:9 to 9:1, to react with a diisocyanate compound. Also, JP 3512183 B and JP 4102627 B disclose grease comprising a specific extreme pressure additive.